Spectroscopy and crystal chemical properties of NaCa2[Si4O10]F natural agrellite with tubular structure

Luminescence of Agrellite Specimen from the Kipawa River Locality

“…Some differences have been observed between the emission spectra of agrellite specimens for various localities presented in [4] or [5] and our results. The main reason for these differences is certainly the difference in REE content, although the data contained in [1,2] are incomplete.…”

“…In [5] for the agrellite sample from Dara-i-Pioz, the emission and excitation spectra of Ce 3+ have been presented. The Ce-content in this sample was 1160-1263 ppm, distinctly less than for the Kipawa River ( Table 1).…”

“…It can be concluded that the crystal-field strength for the Kipawa River specimen is less than for the sample from Dara-i-Pioz. The possibility of Ce 4+ presence and Ce 4+ charge transfer bands on the absorption spectrum at 400 nm, which may be due to the gray color of agrellite crystals, was also assumed [5]. The intensity of the Ce 3+ emission band at 388 nm measured for λexc = 284 nm was almost 1.5 times higher than those observed for λexc = 321 nm, despite the power of the xenon lamp is lower at λ = 284 nm than at 321 nm.…”

“…It can be concluded that the crystal-field strength for the Kipawa River specimen is less than for the sample from Dara-i-Pioz. The possibility of Ce 4+ presence and Ce 4+ charge transfer bands on the absorption spectrum at 400 nm, which may be due to the gray color of agrellite crystals, was also assumed [5].…”

“…The following emission centers have been observed [4]: Ce 3+ , Dy 3+ , and Sm 3+ for samples from the Kipawa River; Fe 3+ , Mn 2+ , Eu 2+ , and presumed Nd 3+ for samples from the Yakutia; and of Ce 3+ and Mn 2+ for specimens from the Dara-i-Pioz. The latest results of spectroscopic investigation of agrellite samples from Dara-i-Pioz (Tajikistan) and Murun massif (Russia) shows luminescence from Ce 3+ and EPR spectra of Mn 2+ [5].…”